Method and apparatus for monitoring physical downlink control channels

Embodiments of the present disclosure generally relate to wireless communication technology, especially to a method and apparatus for discontinuous reception (DRX).

For radio resource control (RRC) connected user equipment (UE) in 5G new radio (NR), a network (e.g., a NodeB) might configure discontinuous reception (DRX) for the purpose of UE side power saving. When DRX is configured, the UE does not need to continuously monitor PDCCH but waits for an on-duration of the DRX cycle and may start to monitor PDCCH during the on-duration. If a PDCCH for the UE is detected during the on-duration, the UE may start a drx-inactivity timer. During the period in which the drx-inactivity timer has yet to expire, the UE may continuously monitor the PDCCH. In other words, the UE enters active time when the drx-inactivity timer is running. When the drx-inactivity timer expires, the UE stops the PDCCH monitoring and enters sleep mode.

Since low power consumption and low data transmission latency is critical in 5G NR, power saving and data transmission latency under DRX retransmission become an important issue to be considered.

Some embodiments of the present disclosure provide at least a technical solution for discontinuous reception implemented between a UE and a NodeB.

Some embodiments of the present disclosure provide a method for monitoring physical downlink control channels (PDCCHs). The method may be performed by a user equipment (UE). The method comprises: receiving a plurality of first configuration sets respectively associated with a plurality of first search space sets; receiving a first indication indicating a group index; and performing PDCCH monitoring in the first search space sets based on a first group configuration indicated by the first indication. Each first configuration set includes a first common configuration and at least one first group configuration

Some other embodiments of the present disclosure provide a method performed by a NodeB. The method comprises: transmitting a plurality of first configuration sets respectively associated with a plurality of first search space sets; and transmitting a first indication indicating a group index. Each first configuration set includes a first common configuration and at least one first group configuration.

Some embodiments of the present disclosure also provide an apparatus, including at least one non-transitory computer-readable medium having computer executable instructions stored thereon, at least one receiver, at least one transmitter, and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiver, and the at least one transmitter. The computer executable instructions are programmed to implement any method as described in the present disclosure, with the at least one receiver, the at least one transmitter, and the at least one processor.

Embodiments of the present disclosure provide a technical solution for discontinuous reception. Accordingly, embodiments of the present disclosure can enhance power saving at the UE side and provide low data latency.

The detailed description of the appended drawings is intended as a description of the currently preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3GPP 5G New Radio (NR), 3GPP long-term evolution (LTE) Release 8 and so on. Persons skilled in the art know very well that, with the development of network architecture and new service scenarios, the embodiments in the present disclosure are also applicable to other similar technical problems.

is a schematic diagram illustrating an exemplary wireless communication system according to some embodiments of the present disclosure.

shows communications between UEs and a NodeB.shows the NodeBand the UEsandfor illustrative purpose. The UEsandmay be under the coverage of the NodeB. As shown in, the NodeBis in communication with the UE. The NodeBis in communication with the UE. In some embodiments, the UEsandmay be RRC connected with the NodeB. The UEsandmay be connected with the NodeBon the RRC layer. The NodeBmay transmit data blocks or data packets to the UEsand. The NodeBmay transmit data blocks or data packets to the UEsandin resource blocks.

For example, the wireless communication system inmay be compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a 3GPP-based network, a 3GPP 5G NR network, a satellite communications network, a high altitude platform network, and/or other communications networks.

In some embodiments, the NodeBmay be referred to as a base station, a base unit, a base, an access point, an access terminal, a macro cell, an enhanced Node B (eNB), a gNB, a Home Node-B, a relay node, a device, a remote unit, or by other terminology used in the art. A NodeB may be distributed over a geographic region. Generally, a NodeB is a part of a radio access network that may include one or more controllers communicably coupled to one or more corresponding base stations.

The UEsandmay include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, and modems), or the like. According to an embodiment of the present disclosure, the UEsandmay include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network. In some embodiments, the UEsandmay include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, the UEsandmay be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described with other terminology used in the art.

When the NodeBtransmits data packets in downlink (e.g., to the RRC connected UEsand). Before data transmission in downlink, the NodeBmay use a physical downlink control channel (PDCCH) to notify the corresponding UE such that the UE may receive data transmission on the corresponding channel.

is a schematic diagram illustrating DRX cycles according to some embodiments of the present disclosure. For the purpose of saving power at the UE side (e.g., UEsand), the NodeBmay apply discontinuous reception (DRX). The waveforminmay include multiple DRX cycles. One DRX cyclemay include an on-durationand an opportunity for DRX. DRX cyclesmay be periodic repetitions of on-durationfollowed by opportunities for DRX(e.g., inactivity periods). The high state of the waveformin an on-durationmay indicate a monitoring statein which a drx-inactivity timer may be activated. The low state of the waveformin an opportunity for DRXmay indicate a non-monitoring statein which a drx-inactivity timer cannot be activated.

It may be assumed that DRX is applied between the NodeBand the UE. The UEdoes not need to continuously monitor the PDCCH, but the UEmay wait for an on-durationof a DRX cycleand wake up to monitor PDCCH. Referring to, the UEmay monitor the PDCCH in the on-duration. The UEmay stop monitoring the PDCCH in the opportunity for DRX. The monitoring stateof the waveformin an on-durationmay indicate that the UEis monitoring the PDCCH. The non-monitoring stateof the waveformin an opportunity for DRXmay indicate that the UEstop monitoring the PDCCH.

During the on duration, if the UEdetects data, aimed at itself, on the PDCCH, the UEmay activate a drx-inactivity timer. When the drx-inactivity timer is activated, the UE enters active time. During the period in which the drx-inactivity timer is activated, the UE is on active time. During the period in which the drx-inactivity timer is activated, the UE may continuously monitor the PDCCH. When the drx-inactivity timer expires or deactivates, the UE may stop monitoring the PDCCH monitoring and enter sleep mode.

5G NR may support a Downlink Control Information (DCI)-based Wake Up Signal (WUS). The WUS may be transmitted before each DRX on-duration. The WUS may indicate whether the UE is requested to wake up and monitor the PDCCH in the subsequent on-duration. If the WUS indicates that the UE is no need to wake up, the UE may enter sleep mode in the subsequent on-duration.

is a schematic diagram illustrating an exemplary DRX scheme supporting DCI-based WUS according to some embodiments of the present disclosure. Persons skilled in the art can understand that the DRX may be applied between the NodeBand any one of the UEsand. For simplicity of explanation, it is assumed hereinafter that DRX is applied between the NodeBand the UE.

The waveforminincludes an on-durationand an active time. The high state of the waveformin an on-durationor an active timemay indicate a monitoring state. The low state of the waveformmay indicate a non-monitoring state.

Referring to, a WUSis received or transmitted before the on-duration. The WUSmay indicate that the UEdoes not have to wake up, and the UEmay stop or omit monitoring of the PDCCH during the on-duration.

In, an eventmay occur during the on-duration. The eventmay indicate arrival of data packets aimed at the UEarrive. In the embodiment of, since the UEis not woken up during the on-duration, the UEmay not receive the data packets of the event, such that the UEmay be required to await the next on-duration for data scheduling.

It can be seen that, the embodiment ofmay further reduce the PDCCH monitoring effort since the WUS is applied. However, since data traffic may occur in bursts, data packets may arrive during an omitted on-duration (e.g., the on-duration). In such a case, the UEmust wait for the next on-duration for the data scheduling. This may increase data transmission latency.

Please refer toagain. Since the data packets targeted for the UEhave to be transmitted, the NodeBmay transmit a WUSbefore the next on-duration. The WUSmay indicate that the UEis requested to wake up. Since the UEreceives the WUStransmitted by the NodeB, the UEmay enter active time. Because the UEenters the active time, the UEmay monitor the PDCCH during the active time.

The time slotson the PDCCH may be with grant, and the NodeBmay schedule the time slotsfor the UE. For example, the NodeBmay use the time slotsto transmit control information to schedule the data transmission for the UE. The time sloton the PDCCH may be without grant, and the NodeBmay not schedule the time slotfor the UE. However, even though the time slotson the PDCCH during the active timemay not be scheduled for the UE(since they are without grant), the UEstill has to monitor the PDCCH for the entire active time. In other words, data scheduling for the UEmay only occur in time slots. After the time slots, there is no scheduling for the UEin the time slots. However, the UEstill has to monitor the PDCCH continuously until the expiry of the active time.

That is, unnecessary PDCCH monitoring can take place during the active time. Especially considering that the drx-inactivity timer may be longer in realistic network configuration, the unnecessary PDCCH monitoring during the active timemay increase. The UEmay have to monitor the PDCCH even in the absence of scheduling for the UEin the active time.

The PDCCH may be monitored in the configured search space sets (e.g., the configured resource blocks). A search space set may be configured to be associated with a control resource set (CORESET). A CORESET may define the time (number of OFDM symbols) and frequency resources to be monitored on the PDCCH. There may be two types of search space sets: common search space sets (CSS) and UE specific search space sets (USS). The CSS may mostly be shared between the UEs and may be configured either in system information or UE specific signalling. The USS may be independently configured for each UE. Up to 10 search space sets, including common search space sets and UE specific search space sets, may be configured for a UE in each bandwidth part. The configuration fields of a search space set and the description of each field are shown in Table 1.

The present disclosure provides schemes to reduce PDCCH monitoring effort during active time and reduce scheduling latency for the arrived data packets.

To reduce PDCCH monitoring effort at the UE side and keep scheduling latency low, the present disclosure provides that, for a set of associated search space sets, the UE may uniformly switch the search space sets from one group configuration to another group configuration. Different group configurations for each search space set may correspond to different PDCCH monitoring efforts.

Multiple group configurations may be configured for each search space set in a plurality of search space sets. Each of the group configurations may have a different group index. Each group configuration may include values of some configuration fields for the search space set. The configuration fields of a group configuration may influence PDCCH monitoring efforts. The values of the other configuration fields (the configuration fields which are not included in the group configurations) remain the same during the switching. In some embodiments, the UE may have a number of group configurations for each search space set in a search space set group; the UE may monitor the PDCCH in a group search space set using the values of the configuration fields of the first group configuration for each search space set at the first timing; and the UE may monitor the PDCCH in the same group of search space sets using the values of the configuration fields of the second group configuration for each search space set at the second timing. The group configurations adopted by the UE for the same group of search space sets are uniformly switched from the first group configurations to the second group configurations.

The search space sets in the same set (or group) may have uniform switching behavior. Exemplary sets (or groups) of search space sets having uniform switching behavior may be provided in the present disclosure.

In one embodiment, all the UE specific search space sets (may or may not associated with same CORESET) may have the same switching behavior. In other words, switching between group configurations may be performed for all the UE specific search space sets at the same time.

In another embodiment, all the common search space sets may have the same switching behavior (may or may not associated with same CORESET). In other words, switching between group configurations may be performed for all the common search space sets at the same time. The common search space sets on which the group configurations can be switched may be the common search space sets which is UE-specifically configured. In other words, if the common search space sets can be configured for a UE, switching between group configurations may be performed on common search space sets.

In another embodiment, all the UE specific search space sets and the common search space sets, which may be configured by a UE, may have the same switching behavior. In other words, switching between group configurations may be performed for all the UE specific search space sets and all the common search space sets (which may be configured for a UE in a UE specific manner) at the same time.

In another embodiment, the search space sets that are associated with the same CORESET may have the same switching behavior. In other words, switching between group configurations may be performed for all the search space sets associated with the same CORESET at the same time.

In yet another embodiment, the search space sets of the same CORESET pool have the same switching behavior. In other words, switching between group configurations may be performed for all the search space sets of the same CORESET pool at the same time.

In yet another embodiment, the search space sets that have the same switching behavior are configured by the network (e.g. a NodeB). In other words, switching between group configurations may be performed for a group of search space sets which is assigned by the network. In some embodiments, the network may configure an index for a plurality of search space sets. The search space sets that are configured with the same index have the same switching behavior. In another embodiments, the network may configure a number of CORESETs and the search space sets associated with these CORESETs have the same switching behavior.

In some embodiments, the configuration fields for a search space set may be divided into two groups: common fields and group-specific fields. Table 2 provides one example of the common fields and group-specific fields divided from the configuration fields for a search space set. The group specific fields may contain the fields relevant to the PDCCH monitoring effort, including the fields regarding monitoring periodicity, monitoring duration and the number of monitoring candidates. The fields in the group-specific fields may be more relevant to saving power for a UE. The fields in the common fields may be less relevant to saving power for a UE.

The common configuration may include the values of the common fields. One group configuration may include the values of the group specific fields. A set of the values for the common fields may be named as a common configuration, and a set of the values for a set of group-specific configuration fields may be named as a group configuration. In each time unit, e.g., a predetermine number of slots, the common configuration and only one group configuration are adopted (or applied) for monitoring the PDCCH in a search space set. The common configurations for a search space set may remain the same during switching between two the group configurations.

In some embodiments, one field may be listed in both the common fields (e.g., the common configuration) and group specific fields (e.g., a group configuration). If both of the common configuration and the group configuration provide values for the same field, the group configuration may override the common configuration, and the value in the group configuration provided for same field may be adopted (applied).

From UE side, a control information on the PDCCH received in any search space set of a plurality of search space sets may have an indication to switch the group configuration in use. Upon the receipt of the control information or the indication on the PDCCH, the UE may switch the group configuration in use to the target group configuration for a group of search space sets. The control information or the indication on the PDCCH may include the group index of the target group configuration. In another embodiment, a scheduling DCI received in a search space set may have an indication to switch the group configuration in use. Upon receipt of the scheduling DCI or the indication in a search space set applied with a group configuration causing less PDCCH monitoring effort, the UE may automatically switch the group configuration in use to the target group configuration for a group of search space sets, in which the target group configuration may causing denser PDCCH monitoring effort.

In one embodiment, one group configuration with a specific group index (e.g., group configuration #0) may be the default group configuration. The default group configuration may be applied at the beginning of a DRX on-duration or at the beginning of active time. In another embodiment, the default group may be configured by the network (e.g., a NodeB).

To reduce the configuration overhead, for each search space set, there may be one group configuration assigned a group index but not configured (i.e., no values are defined or listed in the group configuration). Upon receiving the switching indication to switch to this unconfigured group configuration, the UE may skip or stop monitoring the PDCCH in associated search space sets during the DRX active time. In another embodiment, the UE may skip or stop monitoring the PDCCH in all the search space sets during the DRX active time.

For each search space set of a group of search space sets (on which the switching are uniformly performed), the number of group configurations might be different. In some embodiments, if a received indication is indicative of switching to a specific group configuration, and if this group configuration is not configured for some of the group search space sets, the UE may skip or stop monitoring the PDCCH in the search space sets for which this group configuration is not configured.

is a schematic diagram illustrating search space sets,,, andincluding group configurations according to some embodiments of the present disclosure.

In the embodiment of, CORESETand CORESETmay be configured for a UE. Each of CORESETand CORESETmay be associated with two search space sets. CORESETmay be associated with search space setsand; CORESETmay be associated with search space setsand. Each search space set may be associated with a configuration set. A configuration set may include a common configuration (for the common configuration fields) and N group configurations (from #0 to #N−1, each group configuration is for the group specific configuration fields). Each search space set may be associated with a common configuration (for the common configuration fields) and N group configurations (from #0 to #N−1, each group configuration is for the group specific configuration fields).